Cold chamber shot end with loose piece arrangement



April 19, 1960 A. F. BAUER & 3

COLD CHAMBER SHOT END WITH LOOSE PIECE ARRANGEMENT Filed Jan. 25. 1957 3Sheets -Sheet 1 /JV///////////// lfl/////////// ,9

Fig. 2. /0' /6` /7 Fiq 3 ,5 o

INVENTOR Alfred F. Bauer Aprl 19, 1960 A. F. BAUER COLD CHAMBER SHOT ENDWITH LOOSE PIECE ARRANGEMENT Filed Jan; 23, 1957 3 Sheets-Sheet 2INVENTOR Alfred F. Bauer BY m {g 44 NEY A. F. BAUER April 19, 1960 COLDCHAMBER SHOT END WITH LOOSE PIECE ARRANGEMENT Filed Jan.'23, 1957 5Sheets-Sheet 3 Fig. o.

INVENTOR Alfred F. Bauer ORNEY COLD CHAMBER SHUT END WITH LOOSE PECEARRANGEMENT Application January 23, 1957, Serial No. &35,765 8 Claims.(Cl. 22--200) This invention relates to die casting techniques andimprovements therein.

In the cold chamber process of pressure die casting, one of the inherentdiificulties is mantaining a proper working fit between the shot sleeveand the plunger reciprocable therein. The ideal fit of plunger andsleeve would be one which provides enough clearance so that the slidingmotion of the plunger in the sleeve would result in no binding, gallingor freezing of the two surfaces and at the same time prevents theseepage of molten metal past the face of the plunger into the clearancespace between plunger and sleeve. This ideal condition cannot beattained in actual practice, however. Since the molten metal issubjected to a pressure of several thousand pounds per square inch, sothat it Will be injected into the die cavity properly, some seepage pastthe plunger face will be encountered regardless of how small a clearancespace is provided. Any metal entering this clearance space does notremain molten but chills quickly and solidifies and clings to thesurface of the plunger causing galling and binding of the plunger in thesleeve. This constant wear and tear of shot sleeve and plunger is thebiggest maintenance problem of all cold chamber die casting machines.With improvements in machine structure and casting methods leading tothe production of larger castings requiring the injection of largervolumes of metal, this problem of obtaining and maintaining the properworking fit becomes an increasingly difiicult one.

The larger quantities of metal per shot, of necessity, require the useof larger shot sleeves and plungers. Adequate clearance must be providedbetween the plunger and sleeve at room temperature so that the two willnot stick or freeze when the machine is first started. It is customaryto provide cooling facilities for the plunger in order to solidify thebiscuit of casting metal remaining in the sleeve. Even though the sleevemay also be provided with cooling facilities to help equalze thetemperature between them, the temperature of the two parts Willfiuctuate during operation of the machine. This temperature fiuctuationwill cause a change in the amount of clearance between plunger andsleeve and will lead to excessive galling and sticking as the size ofthese parts is increased. i

i Another inherent problem associated with cold chamber die casting isthat of providing proper lubrication for the plunger and sleeve becauseof the direct contact of these parts With molten metal. The temperatureencountered in these parts are quite high and, therefore, no materialhas been found which aiiords satisfactory lubrication to the slidingcondition existing between plunger and sleeve. Any decrease in theamount of clearance caused by temperature diiferences of plunger andsleeve magnes the lubrication problem as does any accumulation of metalwhich has seeped past the plunger face. It has been found that operatorsfrequently keep their machine Operating longer by using an excess amountof lubricant. This excess lubricant, however, is detri- States atnt Omental to the quality of the casting because it stains its surface,increases porosity and decreases the physical properties of the casting.

Another factor present in the cold chamber process and one which isdfiicult to evaluate is that of friction between the plunger and theshot sleeve. Regardless of the excess amounts of lubricant used, thesurfaces of the plunger and sleeve of currently used machines becomegrooved from wear due to dirt and small bits of metal. The longer themachine is operated, the more these conditions build up resulting inincreased friction between plunger and sleeve. As the f'ictionincreases, more and more of the hydraulic pressure available for theshot is used in overcoming the friction. There is no way of determiningexactly how much of the available pressure is used for this purpose andhow much is left for injecting the molten metal into the die cavity. Onpresent day machines, the operator continues running until the plungerseizes in the sleeve or until a visibly bad casting is produced. Thereis no way for the operator to know when friction between plunger andsleeve has increased to the point where the machine should be stoppedand sleeve and plunger overhauled in order to guarantee high qualitycastings. In the present cold chamber machines the pressure with whichthe metal is injected Varies as the friction condition graduallychanges, resulting in large Variations in the quality of cold chamberdie castings.

It is, therefore, an object of this invention to provide an improvedcold chamber shot sleeve and plunger assembly wherein an interchangeableloose piece or plunger seal separates the plunger tip from the moltenmetal thus avoiding any gallng or sticking of the plunger tip in thesleeve.

Another object of this invention is to provide a cold chamber shotsleeve and plunger assembly with a separate sealing member of a shapedeformable by the molten metal during the injection interval so as topositively assure a tight seal against the shot sleeve and preventseepage.

Still another object of this invention is to provide an assemblage inconformity with the foregoing object, wherein the plunger is finished toa size such that its diameter is materially less than the insidediameter of the shot sleeve so as to eliminate the possibility of theplunger galling and freezing in the shot sleeve.

Another object of this invention is to provide a separate plunger sealin conformity with the foregoing objects by means of which lubricationtor the shot sleeve and plunger can be easily provided and accuratelycontrolled by applying the iubricant to the plunger seal so as toobviate the present practice of overlubricatiou with its resultant illeffects.

Yet another object of this invention is to provide a shot sleeve andplunger assembly wherein a separate scaling member or plunger seal isempioyed in conformity with the foregoing objects so as to obviate anincrease in frictional resistance with succeeding injection Operationsof the plunger.

A further object of this invention is to provide a shot sleeve andplunger assembly wherein a die cast sealing member or plunger seal isinserted in the shot sleeve in the as-cast condition and the `flash isremoved therefrom by the cooperating action of plunger and sleeve thuseliminating a separate trimmng operation.

A still further object of this invention is to provide a shot sleeve andplunger assembly wherein wear and tear of plunger tip and shot sleeveare eliminated.

In the drawings:

Fig. 1 is a sectional view through a portion of a cold chamber diecasting machine, showing details of the chamber as constructed inaccordance with this inven- Patented Apr.. 19, 1960 tion andillustrating in full and dottcd lincs, respectively, the separate loosepiece or scaling member being inserted and in place;

Fig. 2 is a View similar to Fig. 1 but showing the plunger seal in placeand the die casting metal being ladled into the shot chamber;

Fig. 3 is a view similar to Figs. i and 2 but showing the plungcr inposition upon completion of its stroke;

Fig. 4 is an enlarged sectional View illustrating the def ormation ofthe scaling member to cffcct the scaling cngagcment with the inner wallof the shot sle-eve;

Figs. 5-9 are enlarged partial sections illustrating modi- 'ed forms ofscaling members;

' Fig. is a longitudinal section taken through a modifred form of shotchamber assembiy with end loading mechanism; v

Fig. 11 is a pe'spectve view showing an end portion of the shot sleevewith end loading mechanism for the separate plunger seal;

Fig. 12 is a vertical section taken along the plane of section line12-12 inFig. 10;

Fig. 13 is a pcrspcctive view showing a plunger seal as removed from thedie having the gate and flash still attac ed;

Fig. 14 is a perspective view of an alternate modification of the endloading mechanism of the shot sleeve; and

Fig. 15 is a Vertical section taken along the plane of section line15--15 in Fig. 14.

in Pig. l, the reference numeral 10 indicates the fixed die half whereasreference numeral 11 illustrates the movable die half, and referencenumcral 12 indicates a gatc ormed between the two die halves forintroduction of the casting metal into the die cavity. The fixed diehalf in the specific embodiment shown in Fig. 1, tor eX- ample, has anopening 13 therethrough which receives the inner end 14 of the shotsleevc which is indicated generally by the reference character 15. Theshot sleevc has an annular collar portion 16 which bears against theouter face of the fixed die half 10 and is held rigidly thcreagainst bymeans of a front machine plate 17. Reciprocable within the sleeve 15 isa plunger assembly indicated generally by the reference character 1 .8which includes the usual plunger rod 19 and an enlarged plunger headportion 20, the rod being connected at its free end, not shown, to asource of powersuch as a hydraulic ram or the like.

It is to be understood that the particular construction of the diehalves and the manner of securing the shot sleeve to the die halves maytake any convcntional form and the particular structure shown in thedrawings is for illustrative purposes only, with respect to these parts.

l`his invention contemplates the use of a separate scaling member orplunger seal which is preierably made from the same or a closely similarmetal as is being die cast. Since the cold chamber method of die castingis commonly used for aluminum, the separate'plunger seal will preferablybe made of aluminum or an aluminum alloy. l-lowever, it is contemplatedthat plnngcr seals made of metals entirely dissmilar from that beingcast may be used. For example, a ferrous metal or bronze plunger sealmay be used with aluminum cold chamber die castmg.

The separate scaling member or plunger seal in the form of a freefloating piston is indicated generally by the reference character 21which is insertable within the shot sleeve through the usual opening 22thereir. Fig. l illustrates in full line position the plunger seal orsealing member !21 in the process oftbeing inserted within the shot siec/e whcreas the dotted line position shows the seal in place, and Fig. 2shows in full lines the ultimate position of the separate plunger sealbefore the plunger is reciprocated to efiect the injection of the moltenmetal.

With the seal 21 in place, as in Fig. 2, the molten metal 2; isintroduced into the chamber by any suitable means,

such as the ladle iudicated by the reference character 24, and whenproper charge of metal has been poured into the shot chamber, mechanismis opcrated for moving the plunger head 20 in Fig. 3, Fig. 3 showing theposition of the plunger at the end of its stroke and at the completionof the shot.

As shown more clearly in Fig. 4, thesealing member or separate plungerseal may be formed as to provide a disc-like main body portion 25 and`onone side thcreof an annular lip or rim 26 which projects forwardlythere- 'from to provide the central depresson 27 in the piston.Preferably, the lip'26 is so formed that it is thicker in the region 28where it joins the main body 25 than at the free edge portion 29thereof, the purpose of which will be presently apparent. The outersurface of the plunger seal is cylindrical and is initially formed toloosely fit within the shot slccve 15.* For the purpose of lubrication,the outer surface of the plunger seal maybe provided with one or morelubrication'grooves 30 and it is preferred that a suitable lubricant beutilized to coat the piston at least on the outcr cylindrical surfacethereor", some of which lu bricant will, of course, be rctained withinthe lubrication groovcs 30 to prevent undue wear of the shot slccveduring the casting operation.

During the injection interval the injcction 'pressui'e is excrted by theplunger on the casting metal 23 and, be-

ing in the molten or"1iquid state, this pressure is exertcd equally inall directions throughout the body of molten metal. This prcssure actingon the lip or rim 26 ot the plungcr seal will cause it to be deformedoutwardly inthe manner illustrated by solid lines in Fig. 4 so that theouter surface of the plunger seal, at least in the region of the lip orrim, will be in close contact with the shot slecve and thus preventseepage of'mctal pastthe separate plunger seal. Since the plunger sealis of thinnest section at the free edge 29 of the lip or rim 26, thisportion will be aorded the most deformation and the seal will hcncc bemost effectively produced at this point, the pressure of thc moltenmetal 2.3 acting over the entire inner surface area 31 of the lip or rim26 to efiect the deformation thereof.

Prefcrably, the lubrication coating on plunger seal 21 and the scalingmembers hercinafter described is etlected by dipping these parts in anaqueous solution of lubricant while they are hot. 'In thisjmanner, acoat of dry lubricant will be formed on the surface of the scalingmembers. Since these scaling members can easily be made by die casting,the lubrication coat can be conveniently applied by dipping the pieccsas soon as" they are removed from the die and while they are still hot.Thus, the liquid carrier for thelubricant will driven dit' and a drycoating or lubricant will remain. This eliminatcs the formaton of oil orsimilar vapors, when the scaling mem: bers are used in making a shot,which are produced with the lubricants as conventionally used. Onepresent method of lubrication involves the use of a graphite in a liquidcarrier, usually oil, the carrier being used primarily not for anylubricating value since it is vaporized by the molten metal, but asmeans by which the graphite is applied in a liquid state. It would, otcourse,'be incon-V venent and difficult to apply graphite alonein thedry state.

The use of the separate plunger seal 21 permits the plunger head 20 tobe made of material smaller :diameter than the inside diameter of theshot sleeve 15, thus eliminating any wear between plunger and sleeve. InFig. 4, the initial clearance between the plunger seal and shot sleeveas well as the dcformation of the plunger seal has been exaggerated forthe purpose of clarity, although it is to be understood thatthe sameprinciple of operation applied under actual conditions.

Each plunger seal 21 is preferably used only once and then is removedfrom the machine at the same time that the solidificd biscuit 36 ofcasting metal, a-s shown in Fig. 3, is removed from the shot sleeve. Theplunger seal the solidified biscuit and reused several times. Ofcourse,`

if the plunger seal is of some metal dissimilar to that being cast, itwill preferably be reused for a considerable time. This plunger seal maybe fed into the shot sleeve either manually or mechanically as desired.

In actual operation, the plunger seals or sealing members 21 will-permitthe use of much larger cold chambers than has previously beenpracticable. For example, the maximum diameter of shot sleevesconventional now in the art is perhaps 4 inches, whereas with the use ofscaling members such as are disclosed above, the diameter may beincreased to 6, 7 or more inches, thus permitting much larger castingsto be made than were heretofore known.

The reason for this, of course, stems directly from the fact that theplunger seal or sealing member efiectively seals against molten metalleakage past the plunger regardless of the amount of clearance betweenthe plunger and sleeve. At the same time, the lubricating means on theplunger seal provides all of the lubrication that is necessary forproper operation and the attainment of castings having consistently goodquality.

The use of the plunger seal eliminates the variable of friction of theplunger in the shot sleeve since the same amount of friction is presentwith every shot. The plunger seal, being of softer metal than thesleeve, will receive any grooves formed during the injection or rammingoperation of the plunger and since a new piece is used for each shot,identical conditions will be present during each shot. No increasedfriction is cncountered on subsequent shots since there is no contactbetween the plunger and shot sleeve and, the plunger seal prevents theseepage of molten metal into the clearance between plunger and sleeveand consequently there is no build-up of metal particles to retard themovement of the plunger.

' Fgs. 5-9 illustrate modified forms of sealing mernbers for theplunger. In Figs. 6, 7, 8 and 9, the sealing members are of annular formand in general these forms are to be preferred by virtue of the factthat they allow the molten metal to come in contact with the plunger.This is of importance when the plunger is provided with means ofinternal cooling. After the shot of metal has `been injected into thedie, with the metal in the sleeve directly Contacting the end surface ofthe plunger, the coolant in the interier of the plunger absorbs enoughheat from the molten metal to solidify the biscut of metal remaining inthe sleeve, which biscuit is removed with the casting and gate. In allits forms, the plunger seal is z of such a shape as to prevent aV-shaped annular groove in contact with the molten metal so that, ashereinbefore described, the pressure in the molten metal presses theplunger seal against the plunger while deforming its lips and thuscreating a perfect seal against the seepage of molten metal.

The plunger seal of Fig. S is of full piston form with the main bodyportion or hub 42 forming the center of the piston and with an outercylindrcal rim or lip 37 having its thinnest section at the leading edge39. The inner surface 38 of the rim or lip is tapered and it togetherwith the flared web 40 form the V-shaped annular'groove previouslymentioned. Flared web 4@ joins the main body portion or hub 42 topresent a continuous surface between the molten casting metal andplunger 2051. The plunger Zla terminates in the tapered surface 46intersecting the radial shoulder 45 and has a shape similar to that ofthe rear face of the plunger seal. Also, the plunger may be hollow toprovide a coolant chamber 47. In this form, the rim under pressure, willbe de- 6 formed into sealing contact with the inner surface of shotsleeve 15. The position of the parts in Fig. 5 illustrate the positionof the plunger at the end of the shot x when the gate of the castingwill fill the gate runner 12.

The seal of Fig. 6 is similar to that shown in Fig. 5 except that it isannular in form having a cylindrical rim with a tapered' inner surface51 from its leading edge 52 toward the rear edge 53 where it is joinedwith the central hub section 54 which -tapers in the reverse directionas shown to form the V-shaped groove. In both cases the plunger 20:: isthe same.

The plunger seal of Fig. 7 is annular in' general form having an outercylindrical rim or lip 57 with its thinnest section at leading edge 5 9.The V-shaped groove is formed by the tapered inner surface 58 of the rimand the flared web 60. Flared web 60 terminates at its inner edge in acircular hub 61 which under the pressure in jthe molten metal forms aseal against step 64 of plunger Zttb :to prevent seepage of the castingmetal between the plunger seal and plunger. It will be noted that tip 62of plunger 2017 is rounded to increase the cooling area and is providedwith step 65 and tapered surface 66 against which the plunger seal ispressed during the injection operation; i

In the form shown in Fig. 8, the rim 71 tapers inwardly from both theleading and traling edges 72 and 73 and intermediate such edges isformed the inturned radial hub 74 which bears against the front face ofplunger 206, the end of such plunger being shaped to fit the plungerseal as shown.

The plunger seal shown in Fig. 9 consists of an annular band 76 fittingaround the reduced end portion of plunger 20d and hearing againstshoulder '78. The inner surface of the band at leading edge 79 ischamfered as at 81 and this together with chamfered edge 863 of theplunger present an annular space within which the molten metal underpressure may react against the inner surface of the band to expand itand form the proper seal.

Fgs. 10-13 illustrate the principle of automatic flash removal. In Fig.10, 11 is the movable die half, 10 the fixed die half and 12 the gaterunner. The plunger is designated by the numeral 20 and the pouringopening into sleeve 15a by numeral 22::.

As previously mentoned, the forming of the plunger seal lends itselfreadily to a die casting operation. Such a plunger seal 81 is shown inFig. 13, with the gate 82 still attached and having the flash 84thereon. The plunger seals may be formed in dies especially made forthis purpose or one or more plunger seals may be formed in conjunctionwith production run castings, in which case the regular production dieswould be formed with one or more plunger seal cavities attached to theregular casting by means of additional gate runners. In any case, theplunger seals thus formed are preferably used in the as-cast conditionwithout the benefit of any separate trimming operation, such trimrningbeing performed at the time that the plunger seal is used.

For this purpose, the plunger 20 is movable between its bottomedposition and the position in Fig. 10 where it is completely withdrawnfrom the sleeve or cylinder. When withdrawn, the plunger rests upon asemi-circular combined guide and support 85 attached to the sleeve by apair of forwardly projecting arms 86 and 87. An end view showing thelocation of these projecting arms is shown in Fig. 12. The top of thesleeve at its free end is notched inwardly as at 88 leaving therearwardly projecting step 89 upon which the plunger seal rests. Theguide 85 is spaced from the rear edge of the sleeve to provide clearancefor the flash 84 and those portions of the arms 86 and 87 bridging suchgap are bulged outwa'rdly as shown at 90 and 91 in Fig. 11. The plungermust, of course, be capable of withdrawal to such a point to permit theplunger seal to be inserted.

After the plunger seal has been inserted, the plunger is moved inwardlypast the notch 88, after which the.

i the shot sleeve may be modified to accomplish the task of trimming theflash from the plunger seal without; the necessity of performing thisstep on a separate machine.

As in the aforementioned modification, when withdrawn, the plunger rests'upon the semi-circular guide and' support 105. attached to sleeve 15bby a pair of arms 1313 and '115. sleeve end 106 is in a plane which isnormal to the bore of the sleeve and said sleeve end is provided withthree lugs 108, 116 and 112, Fig. 15, which project on the axis of thesleeve. The said lugs perform the 'dual purpose of acting' as locatingblocks for the plunger seal and also serving as a means to shear offsections of the flash and preventing a circular ring of 'fiash'beingformed by the shearing action as the plunger, seal is pushed by theplunger into the end of the sleeve. The guide 185 is spaced from therear ends of the lugs to provide a clearance space 118 for the flash andthose portions of arms 113 and 115 bridging such clearance space arebulged outwardly as shown, at 114- and 116.

' As previously mentioned, the njection of a shot of metal isaccomplished by a two-step operation. After the plunger seal has beeninserted so that it rests upon the locating lugs, the plunger is movedinwardly far enough to push the plungenseal past the free end of thesleeve, after which the shot of metal is poured' into the sleeve andrammed home. movement of the plunger causes the flash to'be sheared fromthe outer diameter of the plunger seal obviating a separate trimmingoperation.

it is to be understood that' the separate plunger seal or sealing membermay be of a shape other than the Again the preliminary specific examplesshown which are for the purpose of illustration andare not meant tolimit the scope of the following claims.

I claim:

1. in the art of pressure die' casting in which a multiplicty, more thanthree, of identical parts are made, the method of produ cing castingsincluding the steps of placing a separate deformable plunger seal into ashot sleeve ahead of the plunger at each cycle of operation of themachine ntroducing molten metal of the same base metal composition assaid seal into said shot sleeve ahead of said plunger seal, exertingpressure upon said plunger, moving said deformable plunger seal andplunger under pressure exerted on the plunger 'forward into' the shotsleeve, deforming the plunger seal by the pressure of the liquid metalinto scaling contact with the inner surface of said sleeve 'and therebypreventing the backward passageofmolten metal between plunger andsleeve, continuing to exert pressure on said plunger and plunger sealwhereby molten metal is forced into the die cavity and solidifiedtherein, and withdrawing said plunger away from said seal and said'soiidied charge, whereby said plunger seal remains as a part of thesoiidified charge.

2. A shot chamber assembly for cold chamber die casting machines,comprising a shot sleeve adapted for connection at one end to a diecasting machine, a plunger within said sleeve and mova'ole between oneposition completely withdrawn from and spaced from the outer end of thesleeve a sufiicient distance to permit the insertion of a plunger sealinto the sleeve and a position innermost within the sleeve, the outeredge of said sleeve being cooperabie with the plunger to shearflash'metal from the periphery of a plunger seal as the plunger is movedfrom its oneposition into the sleeve, andvmeans for supporting saidplunger in an outer position and to guide the same into thevsleeve, saidsupportingmeans shaped i comprising a semi-circular guide and supportmemberattached to the shot sleeve' by a pair of arms.

3. In the art of pressure die casting, the steps of pl'acing a separatedeformable plunger seal of metal selected from' the group consisting ofaluminum and aluminum alloy.

into a shot sleeve ahead of the plunger, introducing molten metal ofsubstantially the same composition as the deformable plunger seal intosaid shot sleeve, exerting pressure upon said plunger, moving saiddeformable plunger seal and plunger under pressure exerted on theplunger forward into the shot sleeve, deforming the plunger seal by thepressure of the liquid metal into scaling contact with the inner surfaceof said sleeve and thereby preventing the backward passage'of noltenmetal between the plunger' and sleevecontinuing' to exert pressure onsaid plunger and plunger seal-whereby molten metal is forced into thedie cavity and solidified therein, and withdrawing said plunger awayfrom said plunger seal and said solidified charge, whereby said plungerseal remains as a part of the solidified charge.

4. In the art of pressure die casting, the method of producing a castingincluding the steps of placing a separate deformable plunger sealconstructed of metal selected from the group consisting of aluminum andaluminum alioy into a shot sleeve ahead of the plunger,introducingmolten metal of substantially the same composition as the deformableplunger seal into said shot sleeve, exerting pressure upon said plunger,moving said deformable,

er seal by the pressure of the liquid metal into scaling;

contact with the inner surface of said sleeve and'thereby preventing thebackward passage of molten metal be.- twe'en plunger and sleeve andcontinuing to eXert pressure on said plunger and plunger seal wherebymolten metal'is forced into the die cavity stopping'the forward rnotionof the plunger while a portion of said molten' metal remains in the gatearea of the apparatus, permittng the molten metal to solidify thereby toform a die' casting, and. withdrawing said plunger away from saidplunger seal and said solidied metal, the plunger seal adhering to themolten metal in the gate areaas it solidifies and being removed from'the die casting apparatus therewith, a separate deformable'plurger sealbeing placed into the shot sleeve as described and the casting stepsrepeated as previously described.

5. In combination, a cold chamber shot sleeve,7 a plunger reciprocablewithin said sleeve, a separate metallic plunger seal engaged against theforward face of said plunger, said seal engagement with the inner end ofsaid sleeve during injection of metal into a die, and having afrusto-concal 'web joining a rear, edge of said rim and forming a V-channel with the inner surface of said rim, said V-shaped channel beingin contact with molten metal 'in said sleeve and subject to deformationby pressure exerted during an injection operation 6. The combinationdefined in claim 5 wherein the:

plunger seal is provided with a disc-like central portion joining saidweb. p V

7. A method of pressure die casting a metallic object which includes,introducing a first deforrnable plunger seal into the shot sleeve of adie casting machine ahead' of a plunger therein, introducing a charge ofmolten etal into said sleeve ahead of said plunger seal, forcing saidplunger and plunger seal forwardly in said sleeve to expel said chargeof metal while still liquid from said sleeve into a die having a cavityfor a production casting and a communicating cavity for a second plungerseal, deforming said first plunger seal into scaling contact with theinner surface of said'sleeve by the pressure of said liquid metal duringthe travel of said plunger, solidifying said charge of molten metal toform a production casting and a second plunger seal, and subsequentlywith draw- 'ing said plunger away from saidfirst plunger seal audincluding a cylindrical rim for scaling' said solidied charge, wherebysaid first plunger seal remains as a part of the solidied charge, andintroducing the second plunger seal formed in said communicating diecavity ahead of said plunger for a succeeding stroke of said plunger asthe first step in a subsequent die casting operation.

8. A method of pressure die casting a metallic object which includes,introdueng a first deformable plunger seal into the shot sleeve of a diecasting machine ahead of a plunger therein, introducing a charge ofmolten metal into said sleeve' ahead of said plunger seal, forcng saidplunger and plunger seal forwardly in said sleeve to expel said chargeof metal while still liquid from said sleeve into a die having a cavityfor a production casting and a communicating cavity for a second plungerseal, deforming said first plunger seal into sealng contact with theinner surface of said sleeve by the pressure of said liquid metal duringthe travel of said plunger, solidifying said charge of molten metal toform a production casting and a second plunger seal, and subsequentlywithdrawing said plunger away from said first plunger seal and saidsolidied charge, Whereby said first plunger seal remains as a part ofthe solidied charge, and introducing the second plunger seal forned insaid communcating die cavity ahead of said plunger for the nextsucceedng 10 stroke of said plunger as the first step in. a subsequentdie casting operation.

References Cited in the file of this patent UNITED STATES PATENTS312,693 Ziegler Feb. 24, 1885 1,730,469 Millspaugh Oct. 8, 19291,781,143 Williams Nov. 11, 1930 1,859,355 Crowther May 24, 19321,935,059 Pack Nov. 14, 1933 1,983,558 Morin Dec. 11, 1934 2,057,669Brauchler Oct. 20, 1936 2,375,486 Morin May 8, 1945 2,468,322 Cook Apr.26, 1949 2,473,366 Galliano June 14, 1949 2,496,131 Morin Ian. 31, 19502,564,885 Sternberg Aug. 21, 1951 2,575,162 Sternberg Nov. 13, 19512,620,528 Sternberg Dec. 9, 1952 2,804,666 Saives Sept. 3, 19572,816,608 Farnwald Dec. 17, 1957 2,836,474 Mosher May 27, 1958 FOREIGNPATENTS 855.010 France Feb. 5, 1940 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent Now &932,865 April 19, 1960 AlfredFerdinand Bauer It is hereby Certified that error appears in the printedspecification of the above numbered patent requiring correction and that'the said Letters Patent should read` as corrected below.

Column 4` line 64 for "material" read materially column 5 line 56, for"prevent" read present Signed and sealed this 20th day of September1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT c. WATSN Attesting Oficer Commissioner of Patents

